Italian policy is that migrants picked up at sea should be returned to Libya by that country's coastguard.

But charities and human rights groups say migrants face appalling conditions in Libya, where abuses at the hands of people-trafficking gangs are rife.

Aquarius had been the last charity rescue ship still operating.

Announcing the decision to end its operations, MSF said EU countries, spearheaded by Italy, had failed to provide enough dedicated rescue capacity of their own, then had actively sabotaged the efforts of others trying to save lives in the Mediterranean, the BBC's Europe correspondent, Damian Grammaticas reports.

In a tweet, MSF Sea said "sustained attacks" by European nations "will mean more deaths at sea, and more needless deaths that will go unwitnessed".

Italy has kept up the pressure. Last month, prosecutors called for the seizure of the Aquarius over the alleged dumping of potentially toxic waste in its ports. MSF called the move "unfounded and sinister".

The Aquarius began operations in 2015 and came to worldwide attention over the summer as Italy closed its ports to migrant rescue ships, leaving the ship stranded at sea with people rescued from the water.

Hundreds of migrants were eventually allowed to disembark in the Spanish port of Valencia in June, after being turned away by Italy and Malta.